In recent years, the development of rice flour breads has been encouraged, so as to increase rice flour consumption. Since gluten contained in wheat flour breads (wheat gluten) is known to cause wheat allergies, rice flour breads made with the use of rice flour as a substitute for wheat flour have drawn attention as foods for patients with the allergies.
Wheat gluten is an important ingredient in producing fluffy, puffed-up breads. In the case of general wheat flour bread making, it is known that water and carbohydrates, such as sugar are added to and kneaded with wheat flour to generate “gluten,” which is rich in viscosity and elasticity, from wheat flour proteins gliadin and glutenin. It is also known that gluten enhances the expansibility and elasticity of bread dough, and thereby wheat flour breads exhibit satisfactory fluffiness and softness after fermentation and baking.
However, in a bread dough comprising rice flour as a sole main ingredient, gluten is not generated after mixing (kneading) the dough. Accordingly, rice flour breads would not be able to rise satisfactorily when the same method of bread making is used as that used for wheat flour breads, meaning that so-called “bread” cannot be made. Thus, most commercially available rice flour breads or commercially available rice flour for making rice flour bread also comprise wheat flour or wheat gluten. Since such products comprise wheat gluten, patients with wheat allergies cannot ingest the same.
There has also been progress in the development of techniques for making gluten-free rice flour breads. Examples of such techniques include: a method of bread making involving the application of a plastic foam molding technique (JP Patent Publication (Kokai) No. 2003-189786 A); methods involving the use of dough comprising gelatinized (“alpha”) rice flour or starch (e.g., JP Patent Publication (Kokai) No. 2006-174822 A and JP Patent Publication (Kokai) No. 2007-215401 A); a method involving the addition of a polysaccharide thickener (JP Patent Publication (Kokai) No. 2005-245409 A); and a method of bread making involving the use of powderization and mixing techniques (JP Patent Publication (Kokai) No. 2006-006200 A). Rice flour breads made by such techniques, however, are significantly inferior to wheat flour breads and rice flour breads made with the addition of gluten in terms of quality, such as fluffiness, softness, or other properties.
In recent years, glutathione, which is deeply associated with oxidoreduction in vivo, has drawn attention as an ingredient allowing recovery of liver functions, detoxication, prevention of cellular senescence, and the like, and it is becoming popular as an ingredient of functional food products such as supplements. Glutathione are contained in, for example, beef liver, spinach, broccoli, and yeast in high amounts. It is known that when reduced glutathione is added to wheat flour breads it acts on wheat gluten and improves wheat flour bread quality (“The Improving Effects of Additives on the Rheology of Wheat Flour Dough: Improving Actions of Ascorbic acid and Glutathion, ” The Bulletin of the Faculty of Bioresources, Mie University, No. 19, pp. 21 to 27 (1997)). However, the effects of glutathione as a food additive ingredient have not yet been thoroughly studied.